Galileo Galilei 1564–1642
Italian astronomer, mathematician, physicist, and philosopher.
Galileo is regarded as one of the greatest scientific thinkers of the Renaissance. His questioning of Aristotelian and Ptolemaic concepts of physics and astronomy, his studies of motion, his refinement of the telescope, and his subsequent discoveries about the universe were to have far-reaching, influential effects on the way people think about the earth and the heavens. Galileo's ideas also got him into trouble: condemned by the Inquisition for espousing a heliocentric world system, which violated Catholic Church teachings that the Earth was the center of the universe, he spent the last years of his life under house arrest.
Galileo Galilei was born in Pisa in 1564 to a cloth merchant/musician and member of the minor nobility. In 1581 he enrolled at the University of Pisa as a medical student, but his interests soon turned to the field of mathematics, and he received a teaching position at the University in 1589. From the beginning, Galileo's strong disagreement with popular Aristotelian theories of motion and gravity led him into conflict with his academic peers, and he was eventually forced to resign as Chair of Mathematics at Pisa. In 1592, however, he was appointed Professor of Mathematics at Padua. On vacation from the University of Padua in 1605 he tutored Cosimo, the Prince of Tuscany. Cosimo was later to become the Grand Duke of Tuscany and Galileo's patron. And it was to the Grand Duke's mother, Christina, that Galileo wrote his fateful Lettera a Madama Cristina de Lorena (written 1615; published 1636; Letter to Madame Christina of Lorraine, Grand Duchess of Tuscany), in which he unsuccessfully attempted to reconcile the Church and Biblical exegesis with the Copemican heliocentric system. Well before this disastrous event, however, a supernova occurred in 1604; it was visible to the human eye and drew Galileo into a heated debate with those who believed in Aristotle's theory that the heavens were immutable. Galileo's life took a decisive turn in 1608 with the invention of the telescope in Holland. A year later, Galileo made refinements to the telescope which allowed him to view not only the stars in the Milky Way but also four moons around Jupiter, spots on the sun, and the rugged and uneven surface of the earth's
moon. Galileo published these findings in Sidereus nuncius (1610; The Starry Messenger) in which he began to think seriously about the likelihood of a Copernican universe. The Starry Messenger was well-received, but a later, more candid discussion of Copernicanism, published in 1613 as Historia e dimonstrazioni intorno alle macchie solari (Sunspot Letters) was condemned by the Church as an outspoken defense of heliocentrism. In 1625, Galileo began working on a discourse entitled Dialogo dei due massimi sistemi del mondo—Tolemaico e Copernicano (1632; Dialogue Concerning the Two Chief World Systems). This venture initially received Pope Urban VIII's blessing as a measured discussion of the compatibility of Church doctrine and the Copernican system. After it was written, however, the Pontiff criticized the Dialogue for two reasons: first, he felt that he himself had been portrayed as an object of ridicule in the discourse; and second, he was notified of the apparent existence of a document signed by Galileo in 1616 promising never again to advocate or even discuss Copernicanism. Events happened fairly quickly after that: In February of 1632, the Dialogue was published; in October of that same year, Galileo was ordered to come to Rome to answer before the Inquisition. In June of 1633, Galileo was compelled to repudiate the Dialogue on his knees before his accusers. He was sentenced as a heretic and condemned to imprisonment for life—a sentence that was softened to house arrest with the understanding that Galileo would never again publish his writings. When he died in 1642, he was blind but still publishing—although outside Italy. To the end of his life, Galileo insisted that there was no conflict between Copernicanism and his own devotion to the Church.
Galileo's major works include The Starry Messenger, which generated much positive excitement when it focused people's eyes for the first time on what was actually happening in the sky. His Sunspot Letters, on the other hand, are notorious. As Stillman Drake points out, Galileo wrote these Letters in Italian rather than in Latin (a scholarly and liturgical language that was universal only to those who were educated); by contrast, the colloquial Letters were accessible to "practically everyone in Italy who could read." Significantly, the arguments contained in them described a Copernican or heliocentric universe rather than the Ptolemaic or world-centered universe advocated by the Church. Galileo's most famous work, the Dialogue Concerning the Two Chief World Systems, is well-known not for its rigid defense of the Copernican against the Ptolemaic system (for it was meant to consider the two impartially); instead, it is infamous because Galileo wrote it after he had apparently been forbidden to write or teach anything at all about the Copernican system. Thus the Dialogue was catalyst for Galileo's appearance and conviction before the Inquisition. Ironically, as Jean Dietz Moss points out, it is the Letter to the Grand Duchess Christina where Galileo unequivocally advocates the Copernican system. Yet he does so while trying to prove that heliocentrism and the interpretation of the Bible are not at odds. Thus, it has "become a classic in literature relating to the conflict between science and religion," and "passages [from it] are often quoted for the sheer power of their expression and the acuity of their observations."
Today, experts on the life and works of Galileo are increasingly coming to believe that he was a victim not of his ideas, but of politics. Several scholars have called into question the very existence of the document of 1616 in which Galileo was supposed to have promised never to teach or write about the Copernican system. Instead, some specialists now argue that the sharptongued and not always diplomatic Galileo became a convenient pawn in a power struggle between members of the Church of Rome as a result of the Counter-Reformation—a time when the Catholic Church was trying to reform itself in response to the Protestant Reformation. As Maurice A. Finocchiaro observes, Galileo's trial occurred "during the so-called Thirty Years War between Catholics and Protestants…." At that time "Pope Urban VIII, who had earlier been an admirer and supporter of Galileo, was in an especially vulnerable position; thus not only could he not continue to protect Galileo, but he had to use Galileo as a scapegoat to reassert … his authority and power."